Identification and hazard analysis of landslides triggered by earthquakes and rainfall

This study aims to utilize the Small Baseline Subset Interferometric Synthetic Aperture Radar(SBAS-In SAR)technique and Google Earth optical remote sensing images to analyze the area within 20 km around the epicenter of a M 3.9, earthquake that occurred in Tanchang County, Gansu Province, on December 28, 2020. The objective is to identify potential earthquake-induced landslides, assess their scale, and determine their impact range. The study results reveal the successful identification of two potential landslides in the 20 km radius around the epicenter. Through time-series deformation analysis, it was observed that these potential landslides were significantly influenced by both the earthquake and rainfall. Further estimation of these potential landslides indicates maximum depths of 7.4 m and 14.1 m for the failure surfaces, with volumes of 9.02 × 10~4m~3and 25.5 ×10~4m~3, respectively. Finally, based on the simulation analysis of Massflow software, the maximum thickness of soil accumulation in the final accumulation area after sliding of the potential landslide in Shangyaai is 12 m, the area of the final accumulation area is 1.75 × 10~4m~2, and the farthest movement distance is 1124 m. The maximum thickness of soil accumulation in the final accumulation area after sliding of the potential landslide in Wangshancun is 8 m, the area of the final accumulation area is 7.89 × 10~4m~2, and the farthest movement distance is 742 m.

The effect of seismic action on stability of saline soil subgrade in cold region based on isothermal stratification method

With the change of seasons, the shear strength of saline soil subgrade filler will change with the change of external temperature, which will aggravate the adverse effects of seismic on the subgrade. To explore the influence of seismic action on the stability of saline soil subgrade under the influence of temperature on the strength of saline soil subgrade filler, this paper first carried out saline soil shear tests at different temperatures to obtain the influence of temperature on the shear strength of saline soil. Then, the temperature field of the saline soil subgrade was simulated, and then based on the subgrade isothermal stratification model and FLAC3D, the displacement and acceleration amplification effects of seismic action on the shady slope, sunny slope and subgrade of saline soil subgrade in different months were analyzed. The following conclusions were finally drawn: under the action of seismic, In the process of the change of subgrade temperature of Qarhan-Golmud Expressway between 7.7°C and 27°C, the change of saline soil cohesion is the main factor affecting the stability of subgrade slope, and the maximum and minimum values of subgrade surface settlement appear in September and June of each year,respectively. In August, the differences of settlement between the shady slope and the sunny slope shoulder of the subgrade were the largest, and the acceleration of the shady slope and the sunny slope and the inside of the subgrade changed most significantly in the vertical direction. Special attention should be paid to the seismic early warning in the above key months;In the range from both sides of the shoulder to the centerline of the roadbed,the acceleration amplification effect starts to increase significantly from about 3m from the centerline of the roadbed to the centerline, so it is necessary to pay attention to the seismic design of this range.

Impact of the Rainfall Intensity and Seepage on Slope Stability in Loess Plateau

In recent years,with the increase of traffic construction in mountainous areas in China,road slope traffic accidents have become more and more common.In addition,natural disasters such as landslides,collapses and subgrade settlements caused by rainfall,driving load,seasonal variation and groundwater distribution are frequent.In particular,rainfall is one of the most common factors leading to slope instability(landslide).Therefore,this paper proposes the seep module based on the application software Geo-studio,and analyzes the slope soil parameters and slope stability under five types of rainfall conditions:light rain(10 mm/d),moderate rain(25 mm/d),heavy rain(50 mm/d),rainstorm(100 mm/d),and torrential rain(250 mm/d).The critical safety factor under rainfall intensity is fitted with nonlinear curve by sine function.The results show that the fitting curve of rainfall intensity and safety factor on the upper slope is excellent.The residual points are evenly distributed in the belt area of±0.1,and the data basically conform to the nonlinear sine model,indicating that the curve plays an essential role in slope health diagnosis.

Coupling action of rainfall and vehicle loads impact on the stability of loess slopes based on the iso-water content layer

To clarify the changes in slope stability of loess slopes under the coupling action of rainfall and vehicle loads.Experiments with different water contents under different environmental conditions were carried out indoors,and the relationship function between water content and shear strength parameters was obtained;based on Geostudio,an equivalent layered calculation model of water content-strength parameters of loess slope was established,the variation law of soil sample matrix suction with volumetric water content was measured by volumetric pressure plate tester.Finally,by using a combination of finite element analysis of saturated/unsatu-rated seepage and limit equilibrium analysis of slope stability,the SLOPE/W module in the modeling software GeoStudio is used to calculate and analyze the effects of vehicle loads,rainfall intensity,rainfall duration,and other working conditions on the stability of loess slopes,respectively.The results show that when the lane is in the middle of the slope,the vehicle load parameters have little effect on the uphill stability,but have a greater impact on the downhill;With the increase in rainfall,the change curves of the slope safety coefficient gradually overlap when the vehicle loads are four-axis,five-axis,and six-axis.This shows that when studying the change of slope safety factor under the dual influence of vehicle loads and rainfall,rainfall is the main cause of slope stability;The change rate of slope safety factor increases gradually with the increase of rainfall,and the change trends of the upper,lower and overall parts of the slope are similar.

Stability of loess high-fill slope based on monitored soil moisture changes

This paper aims to assess the influence of moisture content changes during rainfall on the stability of loess high-fill slopes by taking a loess high-fill slope in Lanzhou City as an example.First,according to the moisture content monitoring data collected from a slope online monitoring system,direct shear tests were performed on soil samples of different moisture content to determine the relationship between the shear strength parameters and moisture content.Next,a coupled hydro-mechanical model with soil shear strength related to moisture content was established and used to analyze 16 working conditions with various rainfall intensities and durations for two cases:shear strength parameters from the site exploration report and those from this study.Finally,the results from the two cases were compared regarding the changes in stresses and displacements after rainfall infiltration to analyze the influence of moisture content on the stability of loess high-fill slopes.The conclusions are as follows:(1)Segmental relationship equations of cohesion and angle of internal friction were established for loess with various moisture content.(2)Under the conditions of different rainfall intensities,significant differences were observed in the trends of slope stress and displacement changes.(3)The slope displacement occurred in the shallow soil layer within about 12.5 m from the slope top,and the plastic strain concentrated in the soil layer within about 6 m from the slope top.(4)The results of slope stability analyses based on moisture content monitoring data are more in line with the observed.